A situation in which it is necessary both to ventilate a patient and to perform a cardiopulmonary resuscitation on that patient frequently occurs in case of the mechanical ventilation of patients, especially in emergency use. The patient is mechanically ventilated, as a rule, via a mask or an endotracheal tube by means of an emergency ventilator.
On the one hand, emergency ventilators, which make the mechanical ventilation of the patient possible in emergency situations, are known from the state of the art. Emergency ventilators are characterized in that they can be used as mobile, portable, autarchic devices independently from external electric power and breathing gas supply. Emergency ventilators are shown in DE 4007361 A1 as well as DE 20315975 U1. In addition, portable and mobile ventilators are known from the field of assisting therapy for both clinical and home use. Thus, DE 8418594 U1 describes a device for acute intervention in asthma, cardiovascular accidents, myocardial infarctions, circulatory symptoms and even for long-term use in the therapy of chronic bronchitis. On the other hand, devices are known that assist the user in performing cardiopulmonary resuscitation (CPR). Cardiopulmonary resuscitation (CPR) is performed by a helping and rescuing person, optionally with assistance of a second person, manually as an alternation between pressure massage of the chest and rescue breathing by means of mouth-to-mouth or mouth-to-nose resuscitation. The alternation between pressure massage and rescue breathing is usually performed at a continuous rhythm of 30 pressure massages of the chest alternating with 2 rescue breaths or at a continuous rhythm of 15 chest massages alternating with 2 rescue breaths until the patient's cardiovascular system resumes functioning on its own, i.e., there is a regular heartbeat again. The rescue breathing is subsequently continued until the patient becomes able to breathe on his own again. We also speak of a 30-to-2 cardiopulmonary resuscitation (CPR), but it has additional variations as well. One person performs alternatingly the chest massages and the rescue breathing in case of the so-called one-rescuer method, and one person performs the chest massage and the second person the rescue breathing in case of the so-called two-rescuer method. Devices, which assist the 30-to-2 rhythm by optical and/or acoustic signal generation and enable the person/persons to concentrate essentially on the performance of the cardiopulmonary resuscitation (CPR) and the patient's status, are available as an aid for the first and/or second person.
Devices for assisting the helping and rescuing persons are described in US 2006 111 749 A1.
Furthermore, training devices and simulators for clinical staff for training in the performance of pressure massage of the chest with correct pressure alternating rhythmically properly with the rescue breathing with correct ventilation (quantity of air) are known. Such training devices and simulators are described in US 2004 058 305 A1.
U.S. Pat. No. 8,151,790 described as another state of the art a valve that may be arranged between a ventilator and a patient for simultaneous use with cardiac massage in order to change the filling of the lungs over time and the pressure in the lungs, as well as the changes in pressure over time in relation to the time frame of inspiration and expiration phases, which time grid is supplied by the ventilator.
A cardiopulmonary device for resuscitating (CPR) a patient for performing cardiac massage and with a device for controlling a ventilator is known from EP0029352 B1. The ventilator is actuated here such that outflow of air from the patient's lungs is prevented from time to time synchronously with the cardiac massage during the transportation of blood from the heart into the patient's body (systole).
U.S. Pat. No. 6,155,257 shows a ventilator as well as a method for operating the ventilator in conjunction with a cardiopulmonary resuscitation (CPR), wherein the ventilation is adapted to the cardiopulmonary resuscitation (CPR). A valve is provided, which is arranged in the gas flow to the patient, in order to delay or prevent the inflow of gas into the patient's lungs until the pressure in the patient's chest cavity has fallen below a predetermined vacuum value relative to the ambient pressure.
When an emergency ventilator is used, the cardiopulmonary resuscitation (CPR) is performed in a usual emergency situation by a helper simultaneously with and superimposed to, but essentially independently from the ventilation. Cardiac massage (CM) is necessary for maintaining the patient's circulatory function in order to supply essentially the brain and other body parts with oxygen by maintaining the blood flow from the heart over the lungs into the body parts to avoid damage, especially permanent damage developing in the brain relatively immediately in case of oxygen deficiency and thus to ensure the supply of oxygen from the lungs into the cells of the body parts and a removal of carbon dioxide from the cells of the body. It is therefore additionally necessary to supply fresh breathing air with a sufficient percentage of oxygen to the lungs. This supply may be achieved by manual rescue breathing by a helper with an oxygen concentration of about 16% or by the use of an emergency ventilator with variable and adjustable oxygen supply.
It is advantageous for the use of cardiac massage that the heart cannot yield when pressing in the chest. Since the possibilities for yielding are limited relatively constantly essentially by the anatomy of the ribs and the organs directly below the chest cavity (stomach, spleen, liver), the expansion space that remains available for yielding is the three-dimensional area of the lungs. Whenever the lungs are emptied completely to the extent that only the so-called functional residual capacity (FRC) is filled with air, i.e., at the end of each expiration phase, the so-called expiration phase, the three-dimensional area in which the heart can yield has its maximum. If the heart in the chest cavity has a possibility of expanding, the effect of the cardiac massage is weaker, despite the application of massive force on the patient's chest by the helper, relative to the delivery of blood from the heart to the body parts, especially the brain, which is brought about by the cardiac massage, than when this space is not available for yielding. As a consequence of this, there is a less effective exchange between the oxygen present in the blood and carbon dioxide and, associated herewith, there is especially a less adequate oxygen supply for the brain, which leads to an increase in the probability of permanent damage for the patient. It is therefore advantageous when performing cardiac massage that the lungs be filled extensively or not emptied substantially during the phase of compression of the cardiac massage, so that the three-dimension area in which the heart can yield is minimized and thus the effect of the cardiac massage and hence indirectly also the pressure of the blood flowing into the body (systolic blood pressure) are increased and the exchange between the oxygen present in the blood and carbon dioxide is improved.
Furthermore, it is advantageous when performing the cardiac massage that the patient's lungs are emptied nearly completely, except for the volume of the functional residual capacity, during the phase of decompression of the cardiac massage, and even a slight vacuum is ideally brought about in the lungs in relation to the ambient pressure in order to assist the backflow of the blood to the heart. Thus assistance arises from the fact that sufficient space is available for the heart and the venous blood vessels leading to the heart in the chest cavity of the patient for the backflow of blood, and the nearly emptied lungs will not fill out this space. An additional aspect is that the blood pressure of the blood flowing back (diastolic blood pressure) is not affected by the ventilation pressure prevailing in the lungs and is possibly increased thereby. As a consequence of the assistance of the backflow of the blood to the heart, an improvement in the blood perfusion and the exchange of blood in the heart as a whole will thus lead indirectly to an improvement of the exchange of oxygen and carbon dioxide in the blood circulation. As a consequence of the improved exchange of oxygen and carbon dioxide in the blood, the risk of permanent damage to the patient, especially to the patient's brain, will decrease. If a conventional cardiopulmonary resuscitation (CPR) is performed according to the one-rescuer method, the 30-to-2 rhythm is used with the use of ventilation through a face mask. Cardiac massage and ventilation are not performed simultaneously here. As soon as an additional rescuer, especially an emergency physician, becomes available in an emergency situation, the mask is replaced with an endotracheal tube, and the endotracheal tube is connected to an emergency ventilator by means of a tube connection. Such an endotracheal tube will be called “tube” for short in the course of the further description of the present application. This has the advantage that the access to the lungs remains free, because it is ensured by the tube that no material aspirated by the patient from the gastrointestinal region can be transported into the patient's lungs during the performance of the rescue breathing. As soon as the access to the patient's airways is ensured, continuous ventilation is performed by means of the ventilator. At the same time, the cardiac massage is continued continuously by a rescuer or a suitable device.
A suitable device for applying the mechanical cardiac massage to the chest of a patient is described, for example, in EP0509773 B1.
The continuous compressions of the chest cavity as the effect of the cardiac massage affect, contrary to the cardiopulmonary resuscitation (CPR) with an alternation between cardiac massage and ventilation, for example according to the 30 (cardiac massages) to 2 (ventilation cycles) rhythm, the 15-to-2 rhythm or the 10-to-2 rhythm, both the manner of filling of the lungs by the ventilator and the resulting pressure changes in the lungs.
Thus, there is a superimposition of the pressure changes of expiration and inspiration, caused by the ventilation and the selected form of ventilation (ventilation mode), and the compressions caused by the cardiac massage in the curve describing the changes in the measured ventilation pressure during the operation of the ventilator. Three general basic ventilation forms, variants of pressure-regulated ventilation forms, variants of volume-regulated ventilation forms, variants of flow-regulated ventilation forms, as well as combinations thereof, for example, a pressure-regulated ventilation form with volume guarantee and maximum flow limitation, are provided by a ventilator according to the state of the art for ventilating a patient. This superimposition due to and of the compressions of the cardiac massage represents an additional marginal condition and an interference variable for the regulation of the ventilation pressure, especially in the pressure-regulated forms of ventilation.